I. Field of the Invention
The present invention relates to the seal elements of hard material of the type in which the seal is made through the precise finishing of the parts themselves. These seal elements are movably installed in direct mutual contact without the interposition of a pliable gasket. Some examples of seal members of this type can be found in the small plates of hard material of faucets, in industrial valves, in the injection pumps of diesel engines, etc. Above all, the following will refer to the case, which is particularly significant, of the small plates for faucets; however, this does not mean that there should be any limitations put on the range of applications of the invention.
II. Description of the Prior Art
The small plates of hard material, used in the regulation of the fluid flow in the faucets for hydraulic systems, are usually made with oxides or silicates of sintered aluminum and then lapped until reflective with a roughness of approximately 0.2 to 0.7 microns. Because of this very precise surfacing treatment, such small plates make up the parts which are suitable for the regulation and interception of the flow of water. Further, because of their hardness, which is o the order of 23,000 N/mm, they last a long time and are able to expel foreign material, even hard material such as granules of sand, which come in contact with them without causing damages. However, the usual processes of sinterization used for this purpose do not allow the small plates of hard material to take on complex forms, for example, having serrations, gear cuttings, comb-like conformations, sub-squarings, or considerable variations of thickness which, in certain cases, could be quite useful. In the past, when such complex configurations were required, one was forced to match a small metal plate of hard material, to which is delegated the function of interception, with an element formed from plastic which has the complex forms needed and which cooperates with the small metal plate of hard material in the intermediate conditions of closing. However, such assemblies, besides offering some assemblage complications, cannot reach the efficiency level that would be offered from a small plate of hard material which in itself has the desired configurations.
Analogous problems are present when similar plates are made of silicon carbide or of tungsten, or of similar materials. It has also been proposed to make the small plates for faucets with a material which is, at least, moderately hard, which, in this case, could be metallic, layered on its operative surface with a harder material--a metallic carbide, a metallic nitride, or carbon with a cubic crystallographic lattice structure--applied through physical or chemical vapor deposition. In this case, the metallic body of the small plate could be made, for example, in a technologically convenient way through shearing from a sheet of stainless steel. However, even in this case, serious limitations of feasible configurations are encountered. Although relatively complex forms can, in fact, be realized, counterbores or parts of varying thickness cannot be obtained.
Some analogous requirements to those facing the small plates of faucets can, in general, be applied to all other seal members made of hard material which are in direct mutual contact.